7. Prices went up because the war broke out. (
because of the fact that the war broke out, Prices went up
8. We won't have to go to school for 3 days later this month. (
We will have 3 days off later this month
9. You must pay a lot to have such a damaged car repaired. (
It costs a lot to have such a damaged car repaired.
10. Perhaps Alex hasn't received my letter. (
It is unlikely that Alex has recieved my letter
11. Thousands of children died of cholera last year. (
Cholera caused death to thousands of children last year
12. Not everyone realized the severity of environmental issues. (
Not everyone were aware of the severity of environmental issues.
13. What makes them lose their hearing permanently? → What is the reason that make them  lose their hearing permanently